Add user guidance on T&D ACC behavior across cost tests (TRC vs SCT) in CET User Guide

Share the following information we were given with CEDARS users:

It is correct that the T&D avoided costs for both electric and gas models will not change between TRC and SCT for annual values. If you look at values levelized over several years, they will change due to the differences in discount rate. However, my understanding is that you are using the annual values so there will be no differences.

Draft for the CET user guide.

Understanding T&D Avoided Costs in Societal Cost Tests

When reviewing Transmission and Distribution (T&D) avoided costs in CEDARS for the Total Resource Cost (TRC) vs Societal Cost Tests (SCB, SCH), here’s what to expect:

Electric and Gas T&D Avoided Costs

The values for T&D avoided costs do not change across different cost tests (such as TRC and SCT) when using annual values. This behavior is expected in CEDARS.

Why is this the case?

Annual T&D avoided costs are not influenced by the differences in discount rates applied across cost tests. Only levelized values, which average costs over multiple years, reflect these discount rate differences and may vary between tests.